Hybrid power converter

ABSTRACT

Power converter circuits, structures, and methods are disclosed herein. In one embodiment, a hybrid converter can include: (i) a first switching device controllable by a control signal; (ii) an inductor coupled to the first switching device and an output; and (iii) a control circuit configured to receive feedback from the output for generation of the control signal to control the first switching device, where the control circuit includes a first detection circuit configured to detect first and second output conditions, the control circuit being configured to operate the first switching device in a switch control in response to the control signal when the first output condition is detected, and to operate the first switching device in a linear control region when the second output condition is detected.

FIELD OF THE INVENTION

The present invention generally relates to the field of semiconductordevices. More specifically, embodiments of the present invention pertainto power converters.

BACKGROUND

Voltage regulators, such as DC-to-DC voltage converters, are used toprovide stable voltage sources for various electronic systems. EfficientDC-to-DC converters are particularly needed for battery management inlow power devices (e.g., laptop notebooks, cellular phones, etc.). Aswitching voltage regulator generates an output voltage by converting aninput DC voltage into a high frequency chopped voltage, and thenfiltering the high frequency chopped voltage to generate the output DCvoltage. Specifically, the switching regulator includes a switch foralternately coupling and decoupling an input DC voltage source (e.g., abattery) to a load (e.g., an integrated circuit (IC)). An output filter,typically including an inductor and a capacitor, may be coupled betweenthe chopped input voltage and the load to filter the output, and thusprovide the output DC voltage. A controller (e.g., a pulse widthmodulator, a pulse frequency modulator, etc.) can control the switch tomaintain a substantially constant output DC voltage.

Another type of converter is a linear regulator, which is suitable forconverters having relatively low input to output voltage differences, aswell as in low power applications where the input to output voltagedifference is high. In a step down application where the input voltageis much greater than the output voltage, a switching regulator typicallyhas better efficiency than a linear regulator due to substantial powerloss in the linear regulator. However, switching regulators may incurpower losses associated with the various switching actions (e.g., powerdevice transitions, driving loss, etc.). In addition, switchingregulator control is typically more complicated than that of a linearregulator, thus consuming more quiescent power. Consequently, switchingregulator efficiency can suffer under relatively light outputconditions, and may become lower than a corresponding linear regulator.

SUMMARY

Embodiments of the present invention relate to hybrid switching andlinear power supply regulators.

In one embodiment, a hybrid converter can include: (i) a first switchingdevice controllable by a control signal; (ii) an inductor coupled to thefirst switching device and an output; and (iii) a control circuitconfigured to receive feedback from the output for generation of thecontrol signal to control the first switching device, where the controlcircuit includes a first detection circuit configured to detect firstand second output conditions, the control circuit being configured tooperate the first switching device in a switch control region inresponse to the control signal when the first output condition isdetected, and to operate the first switching device in a linear controlregion when the second output condition is detected.

In another embodiment, a method of controlling voltage regulation caninclude: (i) monitoring an output of a hybrid converter, the hybridconverter converting an input voltage to an output voltage, themonitored output providing feedback for regulating the output voltage;(ii) controlling a first switching device of the hybrid converter when afirst output condition is detected by turning the first switching deviceon for a first time interval and off for a second time interval; and(iii) controlling the first switching device of the hybrid converterwhen a second output condition is detected by operating the firstswitching device in a linear region.

Embodiments of the present invention can advantageously provide anefficient power conversion supply regulator. Further, embodiments of thepresent invention can accommodate aspects of both switching regulatorsand linear regulators to allow for efficient power supply conversionover a relatively wide range of load conditions. These and otheradvantages of the present invention will become readily apparent fromthe detailed description of preferred embodiments below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block schematic diagram of an example switching regulatorwith a switching device buck topology.

FIG. 1B is a block schematic diagram of an example linear regulator.

FIG. 2 is a block schematic diagram of a first example hybrid converterin accordance with embodiments of the present invention.

FIG. 3 is a block schematic diagram of a second example hybrid converterin accordance with embodiments of the present invention.

FIG. 4 is a block schematic diagram of a third example hybrid converterin accordance with embodiments of the present invention.

FIG. 5A is a block schematic diagram of a fourth example hybridconverter in accordance with embodiments of the present invention.

FIG. 5B is a block schematic diagram of an example variation of thecircuit shown in FIG. 5A, in accordance with embodiments of the presentinvention.

FIG. 6 is a block schematic diagram of a fifth example hybrid converterin accordance with embodiments of the present invention.

FIG. 7A is a block schematic diagram of a sixth example hybrid converterin accordance with embodiments of the present invention.

FIG. 7B is a block schematic diagram of an example variation of thecircuit shown in FIG. 7A, in accordance with embodiments of the presentinvention.

FIG. 8 is a flow diagram of an example method of power conversion usinga hybrid topology in accordance with embodiments of the presentinvention.

DETAILED DESCRIPTION

Reference will now be made in detail to particular embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with thepreferred embodiments, it will be understood that they are not intendedto limit the invention to these embodiments. On the contrary, theinvention is intended to cover alternatives, modifications andequivalents that may be included within the spirit and scope of theinvention as defined by the appended claims. Furthermore, in thefollowing detailed description of the present invention, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. However, it will be readilyapparent to one skilled in the art that the present invention may bepracticed without these specific details. In other instances, well-knownmethods, procedures, processes, components, and circuits have not beendescribed in detail so as not to unnecessarily obscure aspects of thepresent invention.

Some portions of the detailed descriptions which follow are presented interms of processes, procedures, logic blocks, functional blocks,processing, schematic symbols, and/or other symbolic representations ofoperations on code, data bits, data streams, signals, or waveformswithin a computer, processor, controller, device and/or memory. Thesedescriptions and representations are generally used by those skilled inthe data processing arts to effectively convey the substance of theirwork to others skilled in the art. A process, procedure, logic block,function, process, etc., is herein, and is generally, considered to be aself-consistent sequence of steps or instructions leading to a desiredand/or expected result. The steps generally include physicalmanipulations of physical quantities. Usually, though not necessarily,these quantities take the form of electrical, magnetic, optical, orquantum signals capable of being stored, transferred, combined,compared, and otherwise manipulated in a computer or data processingsystem. It has proven convenient at times, principally for reasons ofcommon usage, to refer to these signals as bits, waves, waveforms,streams, values, elements, symbols, characters, terms, numbers, or thelike, and to their representations in computer programs or software ascode (which may be object code, source code or binary code).

It should be borne in mind, however, that all of these and similar termsare associated with the appropriate physical quantities and/or signals,and are merely convenient labels applied to these quantities and/orsignals. Unless specifically stated otherwise and/or as is apparent fromthe following discussions, it is appreciated that throughout the presentapplication, discussions utilizing terms such as “processing,”“operating,” “computing,” “calculating,” “determining,” “manipulating,”“transforming” or the like, refer to the action and processes of acomputer or data processing system, or similar processing device (e.g.,an electrical, optical, or quantum computing or processing device orcircuit), that manipulates and transforms data represented as physical(e.g., electronic) quantities. The terms refer to actions and processesof the processing devices that manipulate or transform physicalquantities within the component(s) of a circuit, system or architecture(e.g., registers, memories, other such information storage, transmissionor display devices, etc.) into other data similarly represented asphysical quantities within other components of the same or a differentsystem or architecture.

Furthermore, in the context of this application, the terms “wire,”“wiring,” “line,” “signal,” “conductor,” and “bus” refer to any knownstructure, construction, arrangement, technique, method and/or processfor physically transferring a signal from one point in a circuit toanother. Also, unless indicated otherwise from the context of its useherein, the terms “known,” “fixed,” “given,” “certain” and“predetermined” generally refer to a value, quantity, parameter,constraint, condition, state, process, procedure, method, practice, orcombination thereof that is, in theory, variable, but is typically setin advance and not varied thereafter when in use.

Light load efficiency in switching regulators may be improved in somecases by turning off a switching regulator for an extensive time duringlight output load conditions. A higher output level may support thisoccurrence, but the output may be substantially unregulated, followed bya drifting back into a regulated output range. However, relatively highoutput noise and relatively slow transient responses may result fromcertain operating conditions, such as during a transition from sleepmode to full power mode.

In one approach, a switching regulator and a linear regulator may becombined in parallel configuration, with an external control signalproviding multiplexing between each regulator type. However, such ascheme can increase digital logic overhead and chip cost due toinclusion of an extra power device in the parallel linear regulator.Particular embodiments can include a hybrid topology and associatedcontrol scheme that operates a power converter in a switching mode underhigh load conditions, and operates the power converter in linear or acombination mode under light load conditions. In this fashion, highefficiency and low noise power conversion over a wide load range can beachieved.

Embodiments of the present invention can advantageously provide anefficient and low noise power conversion regulator. Further, embodimentsof the present invention can accommodate aspects of both switchingregulators and linear regulators in a hybrid configuration to allow forefficient power supply conversion. The invention, in its variousaspects, will be explained in greater detail below with regard toexemplary embodiments.

Any suitable input and regulated output voltages can be accommodated inparticular embodiments. For example, in a buck step down regulator, aninput voltage can range from about 2.5 V to about 5.5 V, such as fromabout 2.7 to about 4.2 V, and including about 4.2 V. A regulated outputvoltage can range from about 0.8 V to abut 2.2 V, and including fromabout 1 V to about 1.8 V, and more specifically about 1.5 V. Forexample, some such voltages can apply in a cell phone application, andmay be utilized for main chip power, random-access memory (RAM) power,or the like. Further, any suitable capacitance and inductance values canbe accommodated in particular embodiments.

In particular embodiments, a hybrid topology and control scheme canoperate a power converter in switching mode under high current loadconditions, and operate the power converter in linear or a combinationmode under light output load conditions. When in switching mode, theswitching devices may be periodically turned off and on based onappropriate feedback-based controls. When in a linear operating mode,one switching device can operate in a linear region to act as a passelement of the linear regulator, and the other switch may be off. In aregulator configuration using two actively controlled switching devices,a second switching device may be turned off, or the second device mayoperate under a linear region to improve output transient responses.When in combination mode, one switching device can operate in a linearregion, and another switching device can operate in a switching mode toimprove output transient responses, as well as overall conversionefficiency.

Referring now to FIG. 1A, shown is a block schematic diagram 100A of anexample switching regulator with a switching device buck topology. Thisexample buck regulator circuit can include one actively controlled powerswitch S1, and one passive power device or rectifier D1. This type ofregulator can be used to convert from a higher (e.g., about 19 V) to alower (e.g., about 5 V) voltage. The active controlled (e.g., viacontrol circuit 102) power switch S1 may be referred to as a “switch” or“switching device,” and may be implemented as any suitable transistor(e.g., NMOS, PMOS, BJT, etc.), or the like.

In operation, when S1 turns on, current in inductor L1 may be increasedand delivered to the output (V_(out) across C_(out)). When S1 turns off,the current in inductor L1 may be decreased and the energy that isstored in inductor L1 during the S1 on state may be delivered to theoutput. When S1 is on, the conduction voltage drop on S1 may berelatively small (e.g., less than about 300 mV). When S1 is off, theremay be no current in S1, and thus no power loss on S1. Further, theconduction voltage drop in a rectifier can be less than about 500 mV,such as when a Schottky rectifier is used. One drawback of this type ofregulator is that a relatively high amount of energy can be used forturning on and off switch S1 because S1 may be a relatively largedevice.

Referring now to FIG. 1B, shown is a block schematic diagram 100B of anexample linear regulator. Here, a single power device S1 is used, andthe conduction drop on S1 may be a difference between the input (V_(in)across C_(in)) and output (V_(out) across C_(out)) voltages. If theinput and output voltage difference exceeds about 300 mV, resultinglinear regulator efficiency tends to be lower than that of acorresponding switching regulator when other loss factors are neglected.However, this type of regulator may be suitable for low cost and lowvoltage difference applications (e.g., converting from about 1.8 V toabout 1.5 V), as well as very light loads on the output node.

In today's switching regulator designs, high frequency operation can beaccommodated to satisfy relatively low cost and small board sizespecifications. However, power losses associated with switching actionsof a switch can be substantial. Such switching losses can includedriving losses of a switch (e.g., switch S1), switching transition losswithin the power switch itself, and magnetic core losses in the inductor(e.g., inductor L1). As a result, switching regulators tend to haverelatively poor power conversion efficiency at very light loadconditions, and in some cases may be lower than linear regulatorefficiency.

As shown in the example power conversion topologies of FIGS. 1A and 1B,switching regulators have more power components than correspondinglinear regulators. Thus if D1 is kept off at relatively light loadconditions, S1 can be operated in a linear mode or region. To accomplishthis, an additional linear regulator loop can be added.

An Exemplary Hybrid Converter

In one example, a hybrid converter can include: (i) a first switchingdevice controllable by a first control signal; (ii) an inductor coupledto the first switching device and an output; and (iii) a control circuitconfigured to receive feedback from the output for generation of thecontrol signal to control the first switching device, where the controlcircuit includes a first detection circuit configured to detect firstand second output conditions, the control circuit being configured tooperate the first switching device in a switch control region inresponse to the control signal when the first output condition isdetected, and to operate the first switching device in a linear controlregion when the second output condition is detected.

Referring now to FIG. 2, shown is a block schematic diagram 200 of afirst example hybrid converter in accordance with embodiments of thepresent invention. Input voltage V_(in) can be converted into outputvoltage V_(out) across capacitor C_(out) by using switch S1, inductorL1, and rectifier D1, with control of switch S1 being provided bycontrol circuit 202. Detection circuit 208 can detect output conditions(e.g., current and/or voltage) to determine when to operate the circuitin a linear mode (e.g., via linear control circuit 206) and when tooperate the circuit in a switching or pulse width modulation (PWM) mode.In particular embodiments, a light output load condition can causemultiplexer 210 to select linear circuit 206 control, and a heavy outputload condition can cause multiplexer 210 to select PWM 204 control. Forexample, a light output load can be from about zero to about 10% of themaximum rated load. For example, a maximum rated load may be about 5 A,a light output load can be in a range of from about 0 mA to about 500mA, while a heavy output load may be in a range of from about 500 mA toabout 5 A.

Switch S1 can operate using control signals from PWM 204, with on andoff control of transistor S1 being for predetermined intervals underheavy load conditions, and a linear mode operation under light loadconditions. In addition to selection of suitable controls for switch S1being passed via multiplexer 210, detection circuit 208 can also sendsignals to PWM 204 and/or linear control 206 to disable circuitry not inuse based on particular output load conditions or mode of operation. Inthis fashion, circuit portions, such as PWM 204 when linear circuit 206control is enabled for light output load operation or linear circuit 206control when PWM 204 control is enabled for heavy output load operation,can be disabled when not in use to reduce power consumption. Inaddition, while control blocks PWM 204 and linear 206 are shownseparately in this example, functional portions thereof can be mergedtogether in certain embodiments.

Multiplexer 210 can be implemented as any suitable type of selectioncircuit (e.g., digital logic, NMOS and/or PMOS transistors, etc.). Also,inductor L1 can have any suitable inductance, such as from about 0.22 uHto about 22 uH. Further, capacitor C_(out) can have any suitablecapacitance, such as from about 4.7 uF to about 2000 uF.

Referring now to FIG. 3, shown is a block schematic diagram 300 of asecond example hybrid converter in accordance with embodiments of thepresent invention. Input voltage V_(in) can be converted into regulatedoutput voltage V_(out) across C_(out) using high side switch S1 and lowside switch S2, and inductor L1, with control of switches S1 and S2being provided by control circuit 302. In this particular examplesuitable for synchronous step down applications, a rectifier (e.g., D1of FIG. 2) may be replaced by actively controlled MOS transistor switchS2. Detection circuits 208 and 310 can determine switching or linearmode operation based on detection of particular output conditions (e.g.,based on voltage, current, etc.). Although circuits 208 and 310 areshown as distinct blocks with unique outputs, these circuits can shareelements, and may have as few as one unique output in certainembodiments.

Under relatively heavy load conditions, switches S1 and S2 can switch ina substantially complementarily fashion according to one or more controlsignals from PWM modulator 304. Under relatively light load conditions,S1 can be controlled via detection circuit 208 and multiplexer 210 tooperate in a linear mode. Switch S2 can enter linear mode viamultiplexer 312 selecting a linear circuit 306 output in response todetection circuit 310, in order to increase output transient responses.Alternatively, S2 may be kept off to simplify control circuit design.For example, if S1 and S2 are to enter the linear mode or the switchingmode simultaneously, detection circuits 208 and 310 may be combined intoone detection circuit in particular embodiments.

Referring now to FIG. 4, shown is a block schematic diagram 400 of athird example hybrid converter in accordance with embodiments of thepresent invention. Detection circuits 208 and 310 can determineswitching or linear mode operation based on output conditions (e.g.,voltage, current, etc.), and control corresponding multiplexers 210 and312, respectively. In this example, control circuit 402 can includeon/off control 424 in place of the linear control connection shown inFIG. 3.

Under relatively heavy load conditions, S1 and S2 can switch in asubstantially complementarily fashion according to one or more controlsignals from PWM modulator 304. Under relatively light load conditions,S1 can be controlled via multiplexer 210 and linear control circuit 306to operate in a linear region. Switch S2 can be turned off (e.g., viaon/off control 424) until detection circuit 310 senses an outputover-voltage condition. Switch S2 may then be turned on to dischargeoutput capacitor C_(out). In this fashion, transient output responsespeed can be increased without substantially increasing switch S1 linearregulator loop complexity.

Referring now to FIG. 5A, shown is a block schematic diagram 500A of afourth example hybrid converter in accordance with embodiments of thepresent invention. This example can represent a more detailed version ofFIG. 2, thus control circuit 502 can include PWM modulator 304 andlinear control 206. In this particular synchronous step down regulatorconfiguration, high side switch S1 can operate in linear mode, while lowside switch S2 remains off under relatively light load conditions.

In operation, output voltage V_(out) can be sensed by feedback erroramplifier (EA) 506 via resistor divider network R1 and R2. A voltagedifference between a sensed output voltage and a reference voltage(V_(REF)) can be filtered and compensated to generate control node onsignal 504. Control signal 504 may then be fed into comparator 512 todetermine whether to enter a first output condition or a second outputcondition mode. Under a first output condition, node 508 from comparator512 may be high to allow tri-state gate driver 514 to pass through anoutput from PWM generator 304 to drive switch S1 on and off periodicallyfor normal switching mode operation. Under this switching modeoperation, switch S2 may be turned on and off in substantiallycomplementarily fashion relative to switch S1. In switching mode, signal508 may be input into linear control 206 to allow the linear controlblock to be shut down in order to reduce power consumption.

Linear control 206 can include transistors Q1, Q2, Q3, and Q4, as wellas resistor R3. Under the second output condition, node 508 fromcomparator 512 may be low, thus turning off tri-state control 514. Atthis point, linear control block 206 can take over gate drive for switchS1 to regulate the output (V_(out)) according to control signal 504 atthe gate of transistor Q4. Transistors Q2 and S1 can be mirroreddevices, and current in Q2 may thus be proportional to S1. When S1provides too much current into the output, output voltage V_(out) mayrise, forcing control signal 504 to go low. This can increase a voltageat node 516, and thus increase a gate voltage of S1. Such an increasedgate voltage can reduce current through S1 to achieve negative feedbackcontrol (e.g., via resistor network R1 and R2 and error amplifier 506).In some cases, in order to help stabilize the linear regulation loop dueto output inductor L1, compensation components (e.g., EA 506) and gaincan be adjusted to achieve good stability margin in linear mode.

Thus, control signal 504 can be used to convey to PWM 304 when toincrease current via driver 514. For example, when V_(out) is lowbecause the output load consumes too much energy, control signal 504 isincreased to cause high side switch S1 current (e.g., as detected bycurrent sensor 510 to provide I_(sen)) to increase. In this fashion,control signal 504 indirectly reveals an output load condition. Inaddition, resistor values for resistors R1, R2, and R3, can range from,e.g., about 1 kΩ to about 1 MΩ.

Referring now to FIG. 5B, shown is a block schematic diagram 500B of anexample variation of the circuit shown in FIG. 5A, in accordance withembodiments of the present invention. Here, the high side switch isdivided into a number of parallel devices or parts, shown here as S1Aand S1B. In this synchronous step down regulator configuration, part ofhigh side switch S1B can turn off, and a remaining part S1A of the highside switch may operate in a linear mode, while low side switch S2 canremain off under light load conditions. The high side switch portionselection can be performed using digital logic, such as AND-gate 516 anddriver 518, but other suitable circuitry can be used in certainembodiments. Under a second output condition, portion S1B can be turnedoff to facilitate loop stability for linear mode operation. Further,quiescent current consumed by control circuit 550 can be reduced usingthis approach.

Referring now to FIG. 6, shown is a block schematic diagram 600 of afifth example hybrid converter in accordance with embodiments of thepresent invention. In this synchronous step down converterconfiguration, under light load conditions, high side switch S1 canoperate in a linear mode, and low side switch S2 can turn on and off inorder to increase output transient response speed, and reduce outputripple. In this example, low side switch control can includeover-voltage protection on the output by changing to on/off control fromPWM 204 during such a condition (e.g., when an external influence causesV_(out) to rise).

Under an output condition when S1 operates in a linear mode, goodtransient response may be difficult to obtain in some cases due torelatively large output inductance L1 (e.g., about 2.2 uH) when usingthe linear loop alone. Thus, switch S2 may be turned on and off based onan output voltage (V_(out)) condition, as determined via resistordivider network R1 and R2. In this particular example, switch S2 may beturned on for a fixed pulse duration generated by timer 606, which canbe initiated by over-voltage comparator 604 providing a related outputnode comparison against a predetermined over-voltage threshold(V_(th2)). In certain embodiments, timer 606 may be optional, but may beadopted to limit a maximum negative inductor current under outputover-voltage conditions.

For example, the on/off control 424 of FIG. 4 can include timer 606 andover-voltage comparator 604 of control circuit 602, and multiplexer 312of FIG. 4 can include AND-gate 608 and driver 610 of control circuit602. The output can be quickly discharged (e.g., in about 10 us) byinductor L1 and switch S2. During such operation, circuit performancecan be greatly improved without substantially increasing complexity ofthe control circuitry. In addition, when high side switch S1 is in alinear mode, low side switch S2 can also be in the linear mode toconfigure a bi-directional linear regulator to speed up output transientresponses.

Referring now to FIG. 7A, shown is a block schematic diagram 700A of asixth example hybrid converter in accordance with embodiments of thepresent invention. In this synchronous step down converterconfiguration, under light load conditions, high side switch S1 canremain off, and low side switch S2 can operate in the linear mode. Lowside switch S2 may operate in a linear mode under a second outputcondition. Here, transistors Q71, Q72, Q73, and Q74, can be used, alongwith resistor R73, to form linear control 706 for linear control on thelow switch side. Control circuit 702 can include PWM 304 control, aswell as low side linear control 706 and tri-state control 704. Also, PWMmodulator 204 can provide signal 708 to driver 710 for control of highside switch S1. This configuration is more attractive for a topologyusing an N-type MOS transistor for high side switch S1 because thelinear control circuitry is simplified under light load conditions.

Referring now to FIG. 7B, shown is a block schematic diagram 700B of anexample variation of the circuit shown in FIG. 7A, in accordance withembodiments of the present invention. Here, the low side switch isdivided into a number of parallel devices or parts, shown here as S2Aand S2B. In this synchronous step down converter configuration, underlight load conditions, high side switch S1, and part (e.g., S2B) of thelow side switch can be held in an off state, and a remaining part (e.g.,S2A) of the low side switch can operate in a linear mode. The low sideswitch portion selection can be performed using digital logic, such asAND-gate 752 and driver 754, but other suitable circuitry can be used incertain embodiments. Thus in this particular example, part (e.g., S2B)of the low side switch may be disabled in the second output condition,and a relatively small portion (e.g., S2A) of the low side switch can beoperated in the linear mode. As a result, loop response speed can beincreased, and quiescent current consumed by the control circuit can bereduced.

Exemplary Method of Controlling Voltage Regulation

In one example, a method of controlling voltage regulation can include:(i) monitoring an output of a hybrid converter, the hybrid converterconverting an input voltage to an output voltage, the monitored outputproviding feedback for regulating the output voltage; (ii) controlling afirst switching device of the hybrid converter when a first outputcondition is detected by turning the first switching device on for afirst time interval and off for a second time interval; and (iii)controlling the first switching device of the hybrid converter when asecond output condition is detected by operating the first switchingdevice in a linear region.

Referring now to FIG. 8, shown is a flow diagram 800 of an examplemethod of power conversion using a hybrid topology in accordance withembodiments of the present invention. The flow begins (802), and anoutput of a hybrid converter can be monitored (804). Such monitoring caninclude current and/or voltage monitoring, such as by using a resistordivider network coupled to an error amplifier. If a light output loadcondition is detected (806), an output switch (e.g., a high side NMOStransistor) can be operated in a linear region (808). On the other hand,if a heavy output load condition is detected, the output switch can beoperated using a PWM modulator for on/off control (810).

While the above examples include circuit and structural implementationsof switching regulators, one skilled in the art will recognize thatother technologies and/or structures can be used in accordance withembodiments. Further, one skilled in the art will recognize that otherdevice circuit arrangements, elements, and the like, may also be used inaccordance with embodiments. For example, although the controllersdescribed above can include a pulse width modulator, particularembodiments are also applicable to other modulation schemes, such aspulse frequency modulation. In addition, while regulators discussedherein include step down and synchronous step down configurations,particular embodiments are also applicable to other voltage regulatortopologies, such as boost converters, synchronous boost converters,flyback, synchronous flyback, and other suitable topologies.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the claims appended hereto and theirequivalents.

1. A hybrid converter configured to convert an input voltage into anoutput voltage that drives an external load, the hybrid convertercomprising: a) a first switching device controllable by a controlsignal; b) an inductor coupled to said first switching device and anoutput; c) a control circuit configured to receive feedback from saidoutput for generation of said control signal to control said firstswitching device, wherein said control circuit comprises a firstdetection circuit configured to detect first and second outputconditions, said control circuit being configured to operate said firstswitching device in a switch control region in response to said controlsignal when said first output condition is detected, and to operate saidfirst switching device in a linear control region using mirroringdevices when said second output condition is detected; and d) a secondswitching device coupled to said inductor, wherein said control circuitfurther comprises a second detection circuit configured to determinewhen said second switching device operates in said switch controlregion, said linear control region, or an off state.
 2. The hybridconverter of claim 1, wherein said control circuit is configured tooperate said second switching device in said linear control region whensaid second output condition is detected.
 3. The hybrid converter ofclaim 1, wherein said control circuit is configured to operate saidsecond switching device in said switch control region when said firstoutput condition is detected.
 4. The hybrid converter of claim 1,wherein said control circuit is configured to operate said secondswitching device in said off state when said second output condition isdetected.
 5. The hybrid converter of claim 1, wherein said controlcircuit is configured, when said second output condition is detected, tooperate said second switching device in said off state when in a firstcontrol mode, and to operate said second switching device in said linearcontrol region when in a second control mode.
 6. The hybrid converter ofclaim 1, wherein said first output condition comprises a heavy outputload and said second output condition comprises a light output load. 7.The hybrid converter of claim 6, wherein said light output loadcomprises an output load of less than about 10% of a maximum loadcurrent on said output.
 8. The hybrid converter of claim 6, wherein saidheavy output load comprises an output load of more than about 10% of amaximum load current on said output.
 9. The hybrid converter of claim 1,wherein said first switching device comprises a plurality of paralleldevices.
 10. The hybrid converter of claim 9, wherein said controlcircuit is configured to operate said first switching device in on andoff regions when said first output condition is detected, and to turnoff a first number of said plurality of parallel devices of said firstswitching device, and to drive a remaining number of said plurality ofparallel devices in said linear control region when said second outputcondition is detected.
 11. The hybrid converter of claim 1, wherein saidcontrol circuit is configured for power savings to disable first circuitportions of said control circuit when said first output condition isdetected, and to disable second circuit portions of said control circuitwhen said second output condition is detected.
 12. The hybrid converterof claim 1, wherein said second switching device comprises a pluralityof parallel devices.
 13. The hybrid converter of claim 12, wherein saidcontrol circuit is configured to turn off a first number of saidplurality of parallel devices of said second switching device, and tooperate a remaining number of said plurality of parallel devices in saidlinear control region when said second output condition is detected. 14.The hybrid converter of claim 12, wherein said control circuit isconfigured to turn off a first number of said plurality of paralleldevices of said second switching device, and to operate a remainingnumber of said plurality of parallel devices in said switch controlregion when said first output condition is detected.
 15. A method ofcontrolling voltage regulation, the method comprising: a) monitoring anoutput of a hybrid converter, said hybrid converter converting an inputvoltage to an output voltage, said monitored output providing feedbackfor regulating said output voltage; b) controlling a first switchingdevice of said hybrid converter to operate in a switch control regionwhen a first output condition is detected by turning said firstswitching device on for a first time interval and off for a second timeinterval; c) controlling said first switching device of said hybridconverter when a second output condition is detected by operating saidfirst switching device in a linear region by using mirroring devices;and d) controlling a second switching device of said hybrid converter byoperating said second switching device in said switch control region,said linear control region, or an off state.
 16. The method of claim 15,further comprising operating said second switching device of said hybridconverter on and off complementary to said first switching device whensaid first output condition is detected.
 17. The method of claim 16,wherein said operation of said second switching device further comprisesturning on said second switching device when said output voltage isabove a predetermined threshold.
 18. The method of claim 15, furthercomprising operating said second switching device of said hybridconverter in said linear control region when said second outputcondition is detected.
 19. The method of claim 18, wherein saidoperation of said second switching device further comprises controllingsaid second switching device in said linear control region when saidoutput voltage is above a predetermined threshold.
 20. A voltageconversion apparatus, comprising: a) means for monitoring an output forproviding feedback for regulating a voltage on said output; b) means forcontrolling a first switching device to operate in a switch controlregion when a first output condition is detected by turning said firstswitching device on for a first time interval and off for a second timeinterval; c) means for controlling said first switching device when asecond output condition is detected by operating said first switchingdevice in a linear region by using mirroring devices; and d) means forcontrolling a second switching device of said hybrid converter byoperating said second switching device in said switch control region,said linear control region, or an off state.